Looks like I had a typo. Firefox was munching it.

the bottom line on this is as D pointed out, $first_name becomes $_POST['first_name']
$last_name becomes $_POST['last_name']

So if you look at your revised, in which you correctly added <1, you will see that the original has a ) that is missing.
They should always be in pairs, those parantheses. So we have 2 ( and then only 1 ) so when php gets to the { it says 'wait a minute....'
Hence, "unexpected {" because it expects a ) first.

so, this is what you want:

PHP Code:
if (strlen($_POST['first_name']) <1)